Power wrenches for threaded connectors such as nuts and bolts are described in U.S. Pat. Nos. 3,706,244 and 2,972,918. The patented tools are especially adapted for flanges whose threaded connectors are arranged in a circular pattern. There is a need for power wrenches, hereinafter sometimes called "tools," which are especially adapted for use on connectors arranged in a straight line or in non-circular patterns, and which can be selectively operated in push or pull modes.
The torque applied on a threaded connector is, of course, the product of the force and the perpendicular distance from the line of action of the force to the axis of rotation. When using a power wrench, the operator must not exceed a maximum prescribed torque to avoid damaging the threaded connection. The wrench actuator is usually a fluid-operated cylinder having a push rod which engages the wrench at a right angle. By limiting the rotation of the wrench to a small angle in response to a full stroke of the push rod, and by making the right angle to become established at the push rod's mid-stroke, the torque can be fairly accurately measured by measuring only the applied pressure in the cylinder. When a tool is designed for a specific connector pattern, the desired right angle between the line of applied force and moment arm can be built into the tool.
It is a broad object of the present invention to provide a new and improved power wrench which is versatile, which easily adapts itself for use on irregular connector patterns, which can work on threaded connectors the access to which is partially obstructed, and which is relatively inexpensive to manufacture.